/*
 * Copyright (C) 2019 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.android.tools.idea.util

import com.intellij.openapi.util.Key
import com.intellij.openapi.util.UserDataHolderEx

/**
 * Returns the value currently associated with [key], falling back to computing it if absent.
 *
 * In the case of a race, [computeValue] may be called but its value not returned from this method.
 */
fun <T : Any> UserDataHolderEx.computeUserDataIfAbsent(key: Key<T>, computeValue: () -> T): T {
  return getUserData(key) ?: putUserDataIfAbsent(key, computeValue())
}
